1. Field of the Invention
The present invention relates to image processing fields, more particularly to video codec methods and systems.
2. Description of Related Art
With continuous advancements in electronics and information technologies and use of internet, remote video surveillance techniques have been developed and used in various applications, e.g., traffic management, security monitoring, or forest fire monitoring. However, users in different types of networks may have different requirements for the video images because different types of networks have different bandwidth performances. Hence, scalable video coding techniques are developed to meet the above requirements.
The scalable video coding (SVC) technique is provided to encode image frames of a video sequence in multiple layers. The first layer, also called base layer (BL), contains a minimum required image data, and the remaining layers, also called enhancement layers (EL), contain the refinements to the data carried by the base layer. This technique makes scalability possible as a receiver can choose to receive only the layers desired and ignore the rest depending on its required resolution and the bit transfer rate capacity of the network.
The spatial scalability is one type of scalable video coding techniques capable of encoding an image frame of a video sequence into two layers at the same frame rate but in different spatial resolutions. The original image of the video sequence is down-sampled to a low spatial resolution base layer image, and the original image is to be coded as the enhancement layer depending on the base layer. Subsequently, the bit stream of the coded base layer is decoded independently, and the bit stream of the coded enhancement layer is decoded based on the reconstructed base layer image. Referring to FIG. 1, there is a block diagram showing a spatial SVC coder in the prior art. An original whole image of size 4xCIF (Common Intermediate Format) is down-sampled by a whole-image down-sampling module 102 to generate a BL whole image of size CIF. A whole-image BL encoder module 106 encodes the BL whole image and generates a BL bit stream and BL data. A whole-image EL encoder module 104 encodes the original whole image and generates an EL bit stream.
In some video monitoring applications, it is only necessary to pay attention to special regions (e.g., doors and windows etc.) in an image and ignore the background regions. In other words, the content of the regions of interest (ROI) may be retained as detailed as possible, while the details of the region of non-interest (non-ROI) may be ignored.
In the current video SVC codec technique, the coding and decoding are performed on the whole video image. But the resolution of the BL image is relatively low, resulting in the loss of details of the image. If the whole image is encoded as the enhancement layer to improve the resolution, the network bandwidth is required to increase to accommodate the higher bit transfer rate. Applications of current video codec technique is, therefore, limited either by the resolution of the image or the bandwidth of the network.
Thus, improvements on the current video codec techniques are desired to overcome the above-mentioned disadvantages and others.